stages: add org.osbuild.anaconda

Add a stage to configure anaconda. For now only the enabled
kickstart modules can be configured. This is done by dropping
a file "90-osbuild.conf" in `/etc/anaconda/conf.d`.

stages/org.osbuild.anaconda

@@ -0,0 +1,58 @@
+#!/usr/bin/python3
+"""
+Configure basic aspects of the anaconda installer
+
+Create an anaconda configuration file `90-osbuild.conf` in
+the folder `/etc/anaconda/conf.d` to configure anaconda.
+
+Currently only the list of enabled kickstart modules is
+configurable via the `kickstart-modules` option.
+"""
+
+import os
+import sys
+
+
+import osbuild.api
+
+
+SCHEMA = """
+"additionalProperties": true,
+"required": ["kickstart-modules"],
+"properties": {
+  "kickstart-modules": {
+    "type": "array",
+    "description": "Kick start modules to enable",
+    "items": {
+      "type": "string"
+    },
+    "minItems": 1
+  }
+}
+"""
+
+CONFIG = """
+# osbuild customizations
+
+[Anaconda]
+# List of enabled Anaconda DBus modules
+kickstart_modules =
+"""
+
+
+def main(tree, options):
+    modules = options["kickstart-modules"]
+    product_dir = os.path.join(tree, "etc/anaconda/conf.d")
+    os.makedirs(product_dir, exist_ok=True)
+
+    with open(os.path.join(product_dir, "90-osbuild.conf"), "w") as f:
+        f.write(CONFIG)
+        for m in modules:
+            f.write(f"    {m}\n")
+
+
+if __name__ == '__main__':
+    stage_args = osbuild.api.arguments()
+    r = main(stage_args["tree"],
+             stage_args["options"])
+    sys.exit(r)